Degradation of polypropylene using ultrasound-induced acoustic cavitation

Cavitation results in generation of hot spots as well as turbulence associated with liquid circulation which can result in degradation of polymeric compounds. In the present work cavitation generated using ultrasound has been utilized for degradation of polypropylene and effect of different operating parameters on the extent of degradation has been investigated. Different concentrations (0.5%, 1% and 1.5%, w/v) and different volumes (50, 75 and 125 ml) were subjected to ultrasonic irradiation using a horn-type reactor. Two different solvents (p-xylene and decalin) have also been used to investigate the dependency of the intensity of cavitation on the type of the solvent. It was found that extent of degradation increases with a decrease in reaction volume and concentration. Use of p-xylene as a solvent resulted in higher extent of degradation. It was also observed that a constant solution viscosity is reached beyond which ultrasonic irradiation could not further degrade polypropylene. The limiting viscosity was also observed to depend on the volume and concentration of polypropylene.